ARM: S3C24XX: Add support UART3 for S3C2443 and S3C2416

Both S3C2443 and S3C2416 support 4 UART channels, this patch adds support
for the missing uart channel.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Signed-off-by: Sangbeom Kim <sbkim73@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>